Automotive air conditioning system evaporators are typically laminated or plate type heat exchangers, in which generally planar, stamped aluminum tube plates are brazed together to create a plurality of flow tubes. The tube plates are brazed together in pairs in a front-to-front orientation, creating thin, flat fluid spaces. To feed fluid in and out of the tubes, integral cups are stamped into the plates, protruding from the back surfaces thereof. When the plates are brazed together, the corresponding cups in each plate align in oppositely directed pairs, and when the completed tubes are assembled to make the evaporator, the pairs of cups line up to create two manifold pipes or passages. In the completed evaporator, the back surfaces of the tube plates of each tube face one another in opposed pairs, and these must be spaced apart by a predetermined distance just sufficient to accommodate corrugated cooling fins or air centers brazed between the tubes. In some evaporator designs, there is an integral cup stamped at each end of each tube plate, creating a manifold pipe at both ends of the completed evaporator. In newer designs, it has been found more efficient to put the cups side-by-side at just one end of each plate, putting the manifold pipes side-by-side at the top end of the completed evaporator. An example of the older design may be seen in coassigned U.S. Pat. No. 4,535,839 to Sacca, and the newer design in coassigned U.S. Pat. No. 5,111,877 to Buchanan et al.
With the older design, with the cups at each end of each plate, it is a relatively simple matter to maintain the necessary cooling fin spacing. Each cup is made to protrude by half the desired fin spacing so that the abutted pairs of cups automatically create the proper spacing. With the newer design, some other structure has to be provided at the noncup end of the plates to maintain the proper fin spacing. A known means for doing so are spacer flanges stamped integrally with the opposite end of the tube plates, projecting in the same direction as the cups, which interfit and abut when the completed tubes are assembled to give the same fin spacing as the cups. One example of a spacer flange design can be seen in U.S. Pat. No. 4,800,954 to Noguchi et al, and another in the Buchanan et al patent just noted above. A problem not articulated in these two references is the necessity for stacking the tube plates evenly as they leave the stamping presses, so that they can be picked up and handled easily during the later assembly and brazing operations. The tube plates are stacked in a back to front orientation, and the cups of consecutive tube plates nest partially into one another, creating a natural stack spacing, which is significantly less than the fin spacing between the completed tubes. In order for the flange ends of the tubes to nest together at all, it is necessary that the flanges not lie exactly perpendicular to the plane of the tube plates. Instead, they are bent out a few degrees to allow each to drop down within the next as they are stacked. Still, the nesting of the flange ends of the tubes can be uneven, because, as the next plate drops down onto the prior, its flanges can slip down too far within the prior plate as the nested cups rock or tilt on each other like spherical bearings. Uneven stacking makes later picking and handling of the tube plates less efficient.